Technical Abstract:
Black sea bass Centropristis striata adapt well to confinement, readily accept formulated feeds, and tolerate temperatures from 5oC - 30oC making them a good candidate for culture in the U.S. Despite this, little is known about their nutrient requirements. As with other marine carnivores, it is presumed black sea bass require high dietary protein. In some species, dietary crude protein (CP) can be reduced through the protein sparing action of other dietary energy sources, particularly lipids. However, feeds with too much energy can reduce intake and affect growth. The objective of this study was to evaluate growth and nutrient utilization in black sea bass fed eight isonitrogenous (45% CP) diets with two sources of protein and four lipid levels (7% ' 16%).
A 2 x 4 factorial with protein source (menhaden or animal protein concentrate) and lipid level (7%, 10%, 13%, and 16%) served as main effects, with a commercial diet (48% CP, 12% lipid) as a control. Twenty fish each (6.0±0.48 g) were stocked into 80-L tanks maintained at 23±0.8oC and a 12 h light: 12 h dark cycle. Fish were fed twice daily at 2.3% biomass day-1 for 10 weeks.
At termination, fish were weighed and analyzed for proximate analysis. Six fish from each experimental unit were analyzed for hepatosomatic index (HSI) and hepatic lipid. Treatments were also evaluated for weight gain (WG), feed efficiency (FE), protein efficiency ratio (PER), energy retention (ER), specific growth rate (SGR), and net protein utilization (NPU).
Protein source, but not lipid level, had a significant affect on weight gain and feed efficiency parameters (P<0.05). Protein source also affected whole body CP, but not whole body lipid. A significant and inverse relationship was detected between whole body CP and whole body lipid with increasing dietary lipid (Fig. 1). No differences were detected in hepatic lipid or HSI.
Data suggest protein sparing is not exhibited in black sea bass fed increasing lipid levels in a 45% CP diet, and dietary lipid greater than 10% has an adverse affect on whole body composition. Dietary lipid should not exceed 10% of the dry diet.